Ultra Wideband (UWB) communication systems have been the focus of increased research in recent years, since such a system can transmit and receive data at an extremely high rate (e.g., from 110 Mb/s to 480 Mb/s in the 10 meter range). It has been predicted that mobile handsets will add UWB functionality around 2007. Many academic papers and patents have been published to target the antenna solution, because the system has a very wide bandwidth (3.1-10.5 GHZ). Most solutions seen to date seek to address the bandwidth concerns without regard to antenna size restrictions. These solutions may therefore be suitable for some devices, for example, PCs and laptop computers, but not for mobile phone handsets and other handheld portable communication devices such as mobile phone handsets, email devices, pocket-sized digital video devices, and the like. Minimum bandwidth and radiation efficiency requirements are a significant challenge for designing UWB antennas for smaller portable communication devices such as those above. Normally, antenna bandwidth and radiation efficiency are proportional to the size of the antenna, so smaller antennas typically exhibit narrow bandwidth and low radiation efficiency.
One conventional antenna that seeks to enable broadband reception in a compact size is described in US Pat. Publication No. 2005/0116867 to Ikmo Park et al (publication date Jun. 2, 2005). That disclosure shows a spiral strip line monopole antenna disposed between a shorted patch antenna and a ground plane. One dielectric substrate lies between the monopole and patch antennas, and another dielectric substrate lies between the ground plane and the monopole antenna. The monopole antenna is quarter wavelength, and the patch is either 11 mm by 11 mm rectangular, or 11 mm diameter round. Small as this may be, it is still seen as to large laterally for some of the more challenging mobile phone handset dimensions currently in use and under development. The tabular design data in that disclosure further shows a height requirement in the 7-10 mm range, resulting in a three dimensional antenna that would be difficult to design into most mobile phone handsets of conventional size. Also, such a tall three-dimensional antenna would reasonably be expected to impose high manufacturing costs.
What is needed is a wideband antenna of very small size, preferably smaller than about 11 mm by 11 mm square, and of low profile to enable use in a variety of mobile communication devices for which physical space is a premium. Advantageously, such an antenna would be simple to manufacture using existing processes so as to hold down incremental costs associated with its manufacture and placement within a completed wireless device.